1. Field of the Invention
The present invention relates to a process for measuring axle or bearing temperatures in order to identify the wheels of railway rolling stocks that are running hot. This invention incorporates infrared temperature receivers and an oscillator that is oriented transversely to the longitudinal direction of the rails, the measured analog values from the infrared receiver being digitized.
2. Description of Related Art
A number of systems for measuring impermissible temperature increases (and in particular for the identification of railway rolling stock wheels that are running hot) are already known. The measuring system itself includes an infrared temperature receiver which is usually located close to the rails so that an active window that subtends an angle to the normal can detect the bearings of a moving railroad car. Only a relatively short period of time is available for temperature measurement, particularly at higher speeds, and rolling stock moving in the longitudinal direction of the rails deviates from rectilinear movement if a straight track has been shifted. This so called "sinusoidal path" leads to a lateral displacement of the axles that having a magnitude on the order of .+-.4 cm. Depending on the design of the bearing, and in particular, the design of the bearing cover, the hottest point that is measurable in a particular bearing design is located at different points. In order to be able to detect all of these deviations of the hottest point of an axle or a bearing transversely to the longitudinal direction of the rails, systems with which a larger area can be detected transversely to the longitudinal direction of the rails have already been proposed in order to be able to detect that particular area of a bearing that is actually too hot, and to be able to do this in a reliable manner. Given an appropriately wide scanning beam transverse to the longitudinal direction of the rail, an integrated signal is obtained which contains the hottest point with certainty. However, the integration that is provided by the detection of a relatively wide area in the longitudinal direction of the axles leads overall to a relatively small difference of the signals that are measured, so that reliable analysis is not possible without some difficulty. In particular, in the case of relatively complete bearing covers, impermissible heating can only be detected over a small part of the axial length of an axle since, by comparison, the other areas are significantly cooler.
In order to widen the possible scanned section along the axis of a bearing, systems that use rotating and oscillating mirrors have been proposed. When these are used, the heating or infrared radiation that occurs along the axle of a railroad car is directed onto an infrared detector and focused. EP-A 265 417 has already proposed the incorporation of a system to widen the image at least on one axis in order to detect overheated wheel bearings in the beam path from the measurement point to the thermal radiation sensor. A system of this kind is formed from a distorting optical element that permits the representation of a correspondingly widened field. Systems that incorporate an oscillating deflection system are described, for example, in EP-A 264 360. On the system, measurement accuracy could be increased since the amplitude of the oscillation of the deflection system has been so selected that a reflection of the cooled detector is picked up at regular intervals by itself in order to arrive at one calibration point for increasing measurement accuracy by this means.